The present invention relates to an impeller for a circumferential current pump, so-called wesco-pump, utilized as a fuel pump capable of being arranged in a tank (intank-type fuel pump, called hereinlater) of, for example, an automobile.
In the known art, there has been utilized an intank-type circumferential current pump capable of being easily mounted to a vehicle such as an automobile and being operative with low noise and at small pressure variation.
FIG. 19 is an illustrated front view, partially in section, showing a circumferential current pump of a conventional structure and FIG. 20 is a sectional view of FIG. 1 in an enlarged scale.
With reference to these FIGS. 19 and 20, a circumferential current pump 51 is one disposed in a fuel tank, not shown, and when an impeller 52 of the pump 51 is rotated by means of a motor 53, energy is applied to the fuel by vanes 54 formed to an outer periphery of the impeller 52 and a pressure of the fuel flowing into a pump passage 56 from a fuel inlet 55 is then increased. The thus pressure-increased fuel is drained on the side of an engine through a fuel drain port 57.
In such circumferential current pump 51, the shape of the vane constituting the inpeller 52 largely affects a pumping performance of the pump 51. Taking the above matter into consideration, the prior art further provides a conventional example (1) such as disclosed in Japanese Patent Laid-open Publication No. SHO 57-206795, which, as shown in FIG. 21 and FIGS. 22A and 22B, discloses an inpeller 52 having an arrangement in which an upstream side surface 60 in a rotational (rotating) direction of one vane 54 and a downstream side surface 61 in the rotational direction of another one vane 54 adjacent to the first (above) mentioned vane 54 are parallel to each other (in other words, opposing surfaces 60 and 61 of a vane groove 58 are parallel to each other).
The prior art still further provides conventional examples such as disclosed in Japanese Patent Laid-open Publication No. HEI 8-100780, which includes an example (2) such as shown in FIG. 23A showing an impeller 52 in which vanes 54, each having a constant thickness, is entirely bent and includes an example (3) such as shown in FIG. 23B showing an impeller 52 in which a front side end of a vane 54 having a constant thickness inclines forward in the rotational direction thereof. In these prior art examples (2), and (3), the length of the vane surface 60 (length of the vane 52 contacting the fuel) by which a centrifugal force is applied to the fuel and the pump drain pressure is increased.
The prior art still further provides conventional examples such as disclosed in Japanese Patent Laid-open Publication No. HEI 6-229388, which includes an example (4) such as shown in FIG. 24 showing an impeller 52, in which an upstream side surface 60 in the rotational direction of a vane 54 is formed entirely in a circular shape and a downstream side surface 61 in the rotational direction thereof extends linearly outward from a radially inner side of the vane 54 to thereby impart a kinetic energy directing to the rotational direction with respect to the fuel in the vane groove by the upstream side surface 60 and hence improve a pumping efficiency.
Further, since the impellers 52 of the respective conventional examples mentioned above always contact the fuels in the tanks, these impellers were formed of resin materials such as phenol resin or PPS resin having excellent resistance to solvent through an injection molding process, and after the injection molding, the side and outer circumferential surfaces were ground and finished so that dimensional performance and/or surface performance are within desired performance ranges, respectively.
The above mentioned prior art examples, however, have still provided the following defects or problems.
In the first example (1), the vane 54 of the impeller 52 is formed so as to provide a thickened portion towards the radially outside portion, so that, as shown in FIG. 22B, a mold is clamped by the vanes 54 which are contracted and deformed after the injection molding (deformation from the solid line position to the dotted line position). Hence, a (mold) releasing resistance at the time of releasing the impeller 53 from the mold is made large, and thus, there is a fear of being hard to remove the impeller 52 from the mold or causing an undesired deformation of the impeller 52 by the releasing resistance.
In the second and third examples (2) and (3), the shape or design of the vane 54 of the impeller 52 is changed to increase the pump drain pressure. However, in such examples, the pump drain pressure cannot be sufficiently increased, and accordingly, further improved technology has been required.
In the fourth example (4), the pumping efficiency is improved by changing the shape or design of the vane 54 of the impeller 52. However, in this example, the pumping efficiency cannot be sufficiently increased, and accordingly, further improved technology has been required.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide an impeller for a circumferential current pump.
This and other objects can be achieved according to the present invention by providing, in one aspect, an impeller for a circumferential current pump including a motor unit section having a motor and a pump unit section operatively connected to the motor unit section through a driving shaft of the motor, the pump unit section including a pump casing, a pump cover and an impeller disposed in a space defined between the pump casing and the cover, the impeller comprising:
a disc-shape member having two surfaces and operatively connected to the motor to be rotatable;
a plurality of vane grooves formed to outer peripheral end portions of both the surfaces in a circumferential direction thereof; and
a plurality of vanes arranged between the respective adjacent vane grooves along a radial direction of the disc-shape member,
wherein each of the vanes has an upstream side surface and a downstream side surface in a rotating direction thereof and a center line between both these surfaces extends along a radial direction of the disc-shape member, the upstream side surface has a radially inside portion and a radially outside portion which are formed to be continuous so that the radially inside portion is in parallel to the center line and the radially outside portion is inclined forward in the rotating direction of the disc-shape member, and the downstream side surface is formed entirely to be parallel to the center line.
In this aspect, only the radially outside portion of the vane is formed to be inclined forward in the rotating direction of the disc-shape member, so that the mold releasing resistance after the injection molding of the impeller can be reduced and, hence, the defective deformation of the impeller due to such releasing resistance can be effectively prevented in comparison with a conventional structure of the impeller in which the upstream side surface of the vane in the rotating direction thereof is entirely inclined forward and the downstream side surface of the vane is entirely inclined in a direction reverse to the rotating direction thereof.
In another aspect of the present invention, there is also provided an impeller for a circumferential current pump including a motor unit section having a motor and a pump unit section operatively connected to the motor unit section through a driving shaft of the motor, the pump unit section including a pump casing, a pump cover and an impeller disposed in a space defined between the pump casing and the cover, the impeller comprising:
a disc-shape member having two surfaces and operatively connected to the motor to be rotatable;
a plurality of vane grooves formed to outer peripheral end portions of both the surfaces in a circumferential direction thereof; and
a plurality of vanes arranged between the respective adjacent vane grooves along a radial direction of the disc-shape member,
wherein each of the vanes has an upstream side surface and a downstream side surface in a rotating direction thereof and a center line between both these surfaces extends along a radial direction of the disc-shape member, the upstream and downstream side surfaces have radially inside portions and radially outside portions which are formed to be continuous respectively, the radially inside portions of the upstream and downstream side surfaces are formed to be parallel to the center line, the radially outside portion of the upstream side surface is inclined forward in the rotating direction and rotating direction of the disc-shape member, and the radially outside portion of the downstream side surface of the vane is formed to be inclined towards a direction reverse to the rotating direction.
In this aspect, only the radially outside portion of the upstream side surface is inclined forward in the rotating direction and only the radially outside portion of the downstream side surface of the vane is formed to be inclined towards a direction reverse to the rotating direction. Accordingly, the releasing resistance after the injection molding of the impeller can be reduced and the defective deformation due to the releasing resistance can be effectively prevented in comparison with a conventional structure of the impeller in which the upstream side surface of the vane in the rotating direction thereof is entirely inclined forward and the downstream side surface of the vane is entirely inclined in a direction reverse to the rotating direction thereof.
Furthermore, in a preferred example of the above aspects of the impeller for a circumferential current pump, the disc-shape member is formed of synthetic resin. The radially outside portion of the upstream side surface of the vane has an arc-shape.
The vane groove formed between the vanes has a radially inside end portion having corner portions, at least one of which is chamfered.
The chamfered structure can also reduce the mold releasing resistance and prevent an occurrence of defective deformation to the impeller due to the releasing resistance.